Abbreviation of the phrase "Bitching in Range." To talk negatively of a certain person/persons, when said party may be present within a distance capable of hearing such accusations. This often leads to an awkward silence, and a brief wave of severe guilt.
Adopted by a clan called 'The Cider-Riders' , the phrase has spread to mainstream use by the students of KEGs, which is a college in a town somewhere near Coventry.
'Remember to always check for BIR prior to bitching.'
Cider-Rider-1: "That Gemma is a right slag, and she's ugly"
Cider-Rider-2: "Shit check for B.I.R!"
*looks behind and all around*
Cider-Rider-1:*whispers* "oooooohmygod shes sitting behind us....."